1. Field of the Invention
The present invention relates generally to a data communication apparatus and method for a CDMA communication system, and in particular, to an apparatus and method for transmitting and receiving data at a high rate.
2. Description of the Related Art
In general, a CDMA (Code Division Multiple Access) system assigns orthogonal codes to separate forward link channels for transmitting voice and data, as shown in Table 1 below. Table 1 shows a method for assigning the orthogonal codes for separating the forward link channels in a CDMA2000 1X system. Here, Walsh codes can be used for the orthogonal codes.
TABLE 1OrthogonalCodeAssignment MethodW064Pilot ChannelW164–W764Paging ChannelW3264Sync ChannelOthersTraffic (Voice/Data) Channel, Common Control Channel
As shown in Table 1, a pilot channel uses a 0th orthogonal code out of orthogonal codes of spreading factor 64, and a paging channel uses 1st to 7th orthogonal codes out of the orthogonal codes of spreading factor 64. Further, a sync channel uses a 32nd orthogonal code out of the orthogonal codes of length 64, and a common control channel and a traffic channel use other orthogonal codes excepting the assigned orthogonal codes.
The Walsh codes used in the CDMA2000 1X system have a 64-chip length, and a set of the used Walsh codes is shown in Table 2 below. In the Walsh code set structure of Table 2, a row indicates a length of a Walsh code for channel spreading one symbol and a column indicates a number (or index) of a Walsh code. The Walsh codes shown in Table 2 have a length of 64 chips and the number of available Walsh codes is 64.
TABLE 2Walsh Chip Within SymbolMODULATION SYMBOL INDEX    
A CDMA2000 system having the Walsh code set of FIG. 2 is a mobile communication system for servicing voice and data. However, the CDMA2000 system adopts a method for servicing the voice and the data using the similar channel structures. That is, the traffic channel includes a fundamental channel and a supplemental channel: the fundamental channel is used to mainly service the voice and the supplemental channel is used to mainly service the data. However, the CDMA2000 1X system requires a channel structure, which can perform a high-rate data service. Accordingly, there is a demand for an apparatus and method, which can provide a data service supporting a higher rate than that of the CDMA2000 1X system and maintain a compatibility with the CDMA2000 system.